init m05e02, in decimal

module05/ex02/adc.c

@@ -0,0 +1,47 @@
+#include "header.h"
+
+// 24.2 : The ADC generates a 10-bit result which is presented in the ADC Data Registers, ADCH and ADCL
+
+void adc_init(uint8_t prescaler_value) {
+    ADMUX = (1 << REFS0);									// Table 24-3 : set voltage reference, AVCC with external capacitor at AREF pin
+    ADCSRA = (1 << ADEN); 									// 24.9.2 : enable ADC
+	ADCSRA |= (1 << ADATE); 								// 24.9.2 : enable Auto Trigger -> it will start a conversion on the selected channel in ADMUX when the selected source (in ADCSRB) is triggered
+	ADCSRA |= (1 << ADIE);								 	// 24.9.2 : enable ADC Interrupt
+    ADCSRA |= ADC_PRESCALE_SET(prescaler_value);			// Table 24-5 : prescaler ADC
+
+	ADCSRB = ADC_TRIGGER_TIMER_1_COMPARE_B;					// Table 24-6 : ADC Auto Trigger Source
+	ADMUX = (ADMUX & 0b11110000) | (adc_channel & 0b1111);	// Table 24-4 : Select ADC channel 0
+}
+
+void adc_print_dec(uint16_t value) {
+	char buffer[17] = {0};
+
+    // handle zero case
+    if (value == 0) {
+        buffer[15] = '0';
+        uart_printstr(&buffer[15]);
+        return;
+    }
+
+	uint8_t pos = 0;
+	while (value) {
+		uint8_t digit = value % 10;
+		buffer[15 - pos] = digit + '0';
+		value /= 10;
+		pos++;
+	}
+	uart_printstr(&buffer[16 - pos]);						// send only from first digit
+}
+
+ISR(ADC_vect) {												// Table 12-6 : interrupt vector for ADC Conversion Complete
+	uint16_t value = ADC;									// 24.9.3.2 : read ADC 16 bits precision
+	adc_print_dec(value);
+	adc_channel = (adc_channel + 1) % 3;					// loop through channels
+	ADMUX = (ADMUX & 0b11110000) | (adc_channel & 0b1111);	// Table 24-4 : Select ADC channel
+	if (adc_channel != 0) {
+		uart_printstr(", ");
+		ADCSRA |= (1 << ADSC);								// 24.9.2 : start next conversion
+	} else {
+		uart_printstr("\r\n");
+	}
+}